The intervertebral disc functions to stabilize the spine and to distribute forces between vertebral bodies. A normal disc includes a gelatinous nucleus pulposus, an annulus fibrosis and two vertebral end plates. The nucleus pulposus is surrounded and confined by the annulus fibrosis.
It is known that intervertebral discs are prone to injury and degeneration. For example, herniated discs are common, and typically occur when normal wear, or exceptional strain, causes a disc to rupture. Degenerative disc disease typically results from the normal aging process, in which the tissue gradually looses its natural water and elasticity, causing the degenerated disc to shrink and possibly rupture.
Intervertebral disc injuries and degeneration are frequently treated by replacing or augmenting the existing disc material. Current intervertebral disc replacement procedures tend to utilize full-sized implants, particularly hydrogels, to augment or replace the original disc nucleus. These materials are commonly implanted after first making a hole with a guide wire, and then subsequently enlarging the hole with a succession of sleeves having increased diameters. Alternatively, a larger hole may be made by surgical incision, using a scalpel or a small diameter coring blade.
One problem associated with such implants is that they require a relatively large hole to be cut in the disc annulus to allow introduction of the implant. Since the hole must be large enough to accommodate a full sized implant, the annulus must be plugged or sewn closed after implantation to avoid allowing the implant to be expelled from the disc. This complicates the procedure, adding surgical time and cost, and leaving a less sound annulus when the procedure is complete.
Moreover, the devices heretofore used to deliver a spinal disc implant have been difficult load and operate.
A need therefore exists for a method of implanting a spinal disc implant that avoids the need to make large incisions in the disc annulus. A need also exists for a delivery device that is easy to load, and that minimizes the need to make a large incision. The present invention addresses those needs.